| As the window of wireless communication system,antenna is responsible for transmitting and receiving electromagnetic energy,and its performance is increasingly strict with the development trend of multi-function,integration and miniaturization of wireless system.In recent years,due to the complexity of the battlefield environment and the rapid development of information technology,the research on aircraft carrying antenna is also facing many challenges.On the one hand,in order to realize spread spectrum communication against electronic interference,the traditional multi-pair narrow-band antenna scheme is no longer applicable,so it is urgent to study the antenna with the characteristics of carrier conformation,ultra-wide working frequency band and miniaturization.On the other hand,to obtain a larger target detection range under the same transmitting system requires the antenna to have higher gain.Therefore,under the requirements of engineering applications,a high gain circular-polarized radial line slot antenna and ultra-wideband miniaturized log-periodic monopole array antenna,which are conformal with the projectile body,are studied and designed in this paper,and their structure and performance parameters are optimized by theoretical analysis,simulation and experiment.The main research work and results of this paper are as follows:1)A high gain circular-polarized radial line slot antenna with beam tilting is realized.The radial waveguide is partially filled with dielectric material layer and fed at its center using a probe with open terminal.Circular polarized slot unit with different length are etched on the upper conductive wall of the waveguide and arranged along a spiral to obtain circular polarized radiation and uniform aperture illumination.In order to improve the radiation efficiency of RLSA,slot pairs with stronger coupling are used at the outer edge of the aperture as matching structure to radiate the residual energy to the free space with the same polarization mode as much as possible.At the same time,in order to meet the requirements of target detection,the main beam of the antenna should be deviated from the broadside direction by 3°.Based on the traditional phased array principle,different beam inclination control methods are studied by analyzing the coaxial mode field transmitted radially outward in the waveguide.Finally,the optimized antenna model was processed and tested,and the results showed that its gain at the central operating frequency of 35GHz was34.08d Bi,the aperture efficiency was over 60%,and the target beam squint angle was achieved.2)A miniaturized log-periodic monopole array antenna covering 10:1 bandwidth is realized,and it is conformal with the target cylindrical carrier successfully.There are fourteen elements with three different types,e.g.conventional monopole,top loaded monopole and folded top loaded monopole,consist the structure of the antenna,the total height of which is 14mm.Elements are arranged along a straight line with log periodic intervals over a metalized ground.In order to obtain the 180°phase difference between adjacent elements and good impedance matching at the feed point,a micro-strip line with modulated impendence function is used to feed the array.In order to achieve carrier conformal,the whole antenna with curving top loaded structure is embedded into the target cylinder and an inclined guided wave structure was introduced at the feed side to improve the radiation pattern of the antenna at the high frequency.The measured results show that the VSWR of the antenna in the frequency band from 2 to 20GHz is less than 2.4,the in-band gain variation range is 3.93d B to 9.35d B,and the overall size is only 1.2×0.47×0.093?_L,?_L,wherel_L is the free space wavelength at the lowest operating frequency. |
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